Fuel and base oil blendstocks from a single feedstock

ABSTRACT

A method comprising providing a fatty acyl mixture comprising: (i) a C 10 -C 16  acyl carbon atom chain content of at least 30 wt. % wherein at least 80% of the C 10 -C 16  acyl carbon atom chains are saturated; and (ii) a C 18 -C 22  acyl carbon atom chain content of at least 20 wt. % wherein at least 50% of the acyl C 18 -C 22  carbon atom chains contain at least one double bond; hydrolyzing the mixture to yield a quantity of C 10 -C 16  saturated fatty acids and C 18 -C 22  unsaturated fatty acids; oligomerizing at least some of the C 18 -C 22  unsaturated fatty acids to yield a quantity of C 36+  fatty acid oligomers; hydrotreating at least some of the C 10 -C 16  saturated fatty acids and at least some of the C 36+  fatty acid oligomers to yield a quantity of diesel fuel blendstock and C 36+  alkanes; and separating at least some of the diesel fuel blendstock from the C 36+  alkanes.

TECHNICAL FIELD

The invention relates generally to methods for making transportationfuel and base oil blendstocks from biomass-derived compositions.

BACKGROUND

Transportation fuel and base oil blendstocks produced from biomass areof increasing interest since they are derived from renewable resourcesand may provide an attractive alternative and/or supplement to similarpetroleum-derived products. Conventional processes for producing fueland base oil blendstocks from biomass often employ separate fuel andbase oil trains requiring duplicate reactors (and associated equipment)and the production of fuels has typically required a hydroisomerizationstep.

Conventional approaches for converting vegetable oils or other fattyacid derivatives into transportation fuels may comprisetransesterification, catalytic hydrotreatment, hydrocracking, catalyticcracking without hydrogen, and thermal cracking, among others.

Triglycerides may be transesterified to produce a fatty acid alkylester, most commonly a fatty acid methyl ester (FAME). Conventional FAMEis primarily composed of methyl esters of C₁₈₊ saturated fatty acids.The poor low temperature properties of conventional FAME however havelimited its wider use in regions with colder climatic conditions.Generally, the introduction of at least one double bond into the FAMEmolecule is needed in order to improve its low temperature properties.However, FAME molecules derived from unsaturated fatty acids contributeto poor oxidation stability of the fuel and to deposit formation.

Triglycerides may be hydrotreated to conventionally produce a normalC₁₈₊ paraffin product. However, the poor low temperature properties ofthe normal C₁₈₊ paraffin product limit the amount of product that can beblended in conventional diesel fuels in the summer time and prevent itsuse during the winter time. The normal C₁₈₊ paraffinic product may befurther isomerized to a C₁₈₊ isoparaffinic product in order to lower thepour point.

There is a need to develop methods for efficiently processing, oftensimultaneously, biomass-derived compositions into a broader range oflubricants and fuel types having improved low temperature propertieswherein the lubricants and fuels may be produced with reduced capitalequipment requirements and with reduced hydrogen consumption.

SUMMARY OF THE INVENTION

In one embodiment, the invention relates to a method comprising thesteps of providing a fatty acyl mixture comprising: (i) a C₁₀-C₁₆ acylcarbon atom chain content of at least 30 wt. % wherein at least 80% ofthe C₁₀-C₁₆ acyl carbon atom chains are saturated; and (ii) a C₁₈-C₂₂acyl carbon atom chain content of at least 20 wt. % wherein at least 50%of the acyl C₁₈-C₂₂ carbon atom chains contain at least one double bond;hydrolyzing at least some of the mixture to yield a quantity of C₁₀-C₁₆saturated fatty acids and C₁₈-C₂₂ unsaturated fatty acids; oligomerizingat least some of the C₁₈-C₂₂ unsaturated fatty acids to yield a quantityof C₃₆₊ fatty acid oligomers; hydrotreating at least some of the C₁₀-C₁₆saturated fatty acids and at least some of the C₃₆₊ fatty acid oligomersto yield a quantity of diesel fuel blendstock and C₃₆₊ alkanes; andseparating at least some of the diesel fuel blendstock from the C₃₆₊alkanes.

The foregoing has outlined rather broadly the features of the inventionin order that the detailed description of the invention that follows maybe better understood. Additional features and advantages of theinvention will be described hereinafter which form the subject of theclaims of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the invention, and the advantagesthereof, reference is now made to the following descriptions taken inconjunction with the accompanying drawing, in which:

FIG. 1 depicts a process flow diagram of an embodiment of the invention.

DETAILED DESCRIPTION

The following terms will be used throughout the specification and willhave the following meanings unless otherwise indicated.

The term “biologically-derived oil” refers to anytriglyceride-containing oil that is at least partially derived from abiological source such as, but not limited to, crops, vegetables,microalgae, animals and combinations thereof. Such oils may furthercomprise free fatty acids. The biological source is henceforth referredto as “biomass.” For more on the advantages of using microalgae as asource of triglycerides, see R. Baum, “Microalgae are Possible Source ofBiodiesel Fuel,” Chem. & Eng. News, 72, 28-29 (1994).

The term “fatty acyl” refers to a generic term for describing fattyacids, their conjugates and derivatives, including esters, andcombinations thereof. Fatty acyls encompass the esters derived from thereaction of fatty acids with alcohols. These esters may include fattyacid alkyl esters, such as fatty acid methyl esters, and fatty acidesters of glycerol, such as mono, di, and triglycerides. In thetriglycerides, the three hydroxyl groups of glycerol are esterified.

The term “fatty acid” refers to a class of organic acids, having between4 and 24 carbon atoms, of the general formula:

wherein R is generally a saturated (alkyl)hydrocarbon chain or a mono-or poly-unsaturated (alkenyl or olefinic) hydrocarbon chain.

The term “acyl carbon atom chain” denotes the —C(═O)R group, wherein Ris as defined above. Thus, for example, lauric acid which has thestructure

may be described as having a C₁₂ acyl carbon atom chain.

The term “triglyceride” refers to a class of molecules having thefollowing molecular structure:

where x, y, and z can be the same or different, and wherein one or moreof the branches defined by x, y, and z can have unsaturated regions.

The term “oligomerization” refers to the additive reaction of like orsimilar molecules (i.e., “mers”) to form a larger molecule. For example,unsaturated fatty acids can react or combine via the double bonds intheir structures. When two such species combine to form a largermolecule, the resulting species is termed a “dimer.” When, for example,the aforementioned fatty acid components contain multiple regions ofunsaturation, oligomers comprised of three or more mers are possible(e.g., “trimers”).

The term “hydroprocessing” refers to processes wherein ahydrocarbon-based material reacts with hydrogen, typically underpressure and with a catalyst (hydroprocessing can be non-catalytic).Such processes include, but are not limited to, hydrodeoxygenation (ofoxygenated species), hydrotreating, hydrocracking, hydroisomerization,and hydrodewaxing. Examples of such processes are disclosed in U.S. Pat.No. 6,630,066 and U.S. Pat. No. 6,841,063. Embodiments of the inventionutilize such hydroprocessing to convert fatty acyls to paraffins. Theterms “hydroprocessing” and “hydrotreating” are used interchangeablyherein.

The term “hydroisomerization” refers to a process in which a normalparaffin is converted at least partially into an isoparaffin by the useof hydrogen and a catalyst. Isomerization dewaxing catalysts arerepresentative catalysts used in such processes (see U.S. Pat. No.5,300,210; U.S. Pat. No. 5,158,665; and U.S. Pat. No. 4,859,312).

The term “transportation fuels” refers to hydrocarbon-based fuelssuitable for consumption by vehicles. Such fuels include, but are notlimited to, diesel, gasoline, jet fuel and the like.

The term diesel fuel refers to hydrocarbons having boiling points in therange of from 350° F. to 700° F. (177° C. to 371° C.).

The term “base oil” refers a hydrocarbon fluid having a kinematicviscosity at 100° C. between 1.5 and 74.9 mm²/s. It is a hydrocarbonfluid to which other oils or substances may be added to produce alubricant. Base oils are generally classified by the American PetroleumInstitute (API Publication Number 1509, Appendix E) into one of fivegeneral categories: Group I base oils contain <90% saturatesand/or >0.03% sulfur and have a viscosity index ≧80 and <120; Group IIbase oils contain ≧90% saturates and ≦0.03% sulfur and have a viscosityindex ≧80 and <120; Group III base oils contain ≧90% saturates and≦0.03% sulfur and have a viscosity index ≧120; Group IV base oils arepolyalphaolefins; Group V base oils include all other base oils notincluded in Group I, II, III, or IV.

The term “cloud point” refers to the temperature of a liquid when thesmallest observable cluster of hydrocarbon crystals first occurs uponcooling under prescribed conditions (see ASTM D2500).

The term “C_(n)” refers to a hydrocarbon or hydrocarbon-containingmolecule or fragment (e.g., an alkyl or alkenyl group) wherein “n”denotes the number of carbon atoms in the fragment or moleculeirrespective of linearity or branching. The term “C₃₆₊” refers to ahydrocarbon or hydrocarbon-containing molecule or fragment having 36 ormore carbon atoms in the molecule or fragment.

1. Compositions: In one embodiment, the invention relates to providing afatty acyl mixture comprising: a C₁₀-C₁₆ acyl carbon atom chain contentof at least 30 wt. % wherein at least 80% of the C₁₀-C₁₆ acyl carbonatom chains are saturated; and a C₁₈-C₂₂ acyl carbon atom chain contentof at least 20 wt. % wherein at least 50% of the acyl C₁₈-C₂₂ carbonatom chains contain at least one double bond.

In a first sub-embodiment, the fatty acyl mixture has a C₁₀-C₁₆ acylcarbon atom chain content of at least 40 wt. %; in a secondsub-embodiment, a C₁₀-C₁₆ acyl carbon atom chain content of at least 50wt. %; in a third sub-embodiment, a C₁₀-C₁₆ acyl carbon atom chaincontent of at least 60 wt. %; in a fourth sub-embodiment, a C₁₀-C₁₆ acylcarbon atom chain content of at least 70 wt. %; in a fifthsub-embodiment, a C₁₀-C₁₆ acyl carbon atom chain content of no more than80 wt. %.

In a sixth sub-embodiment, the fatty acyl mixture has a C₁₈-C₂₂ acylcarbon atom chain content of at least 30%; in seventh sub-embodiment, aC₁₈-C₂₂ acyl carbon atom chain content of at least 40 wt. %; in aneighth sub-embodiment, a C₁₈-C₂₂ acyl carbon atom chain content of atleast 50 wt. %; in a ninth sub-embodiment, a C₁₈-C₂₂ acyl carbon atomchain content of at least 60 wt. %; in tenth sub-embodiment, a C₁₈-C₂₂acyl carbon atom chain content of no more than 70 wt. %.

In one embodiment, the fatty acyl mixture is a biologically-derived oilwhich originates from a biomass source selected from the groupconsisting of crops, vegetables, microalgae, animal sources andcombinations thereof. Those of skill in the art will recognize thatgenerally any biological source of fatty acyl compounds can serve as thebiomass from which the biologically-derived oil can be obtained. It willbe further appreciated that some such sources are more economical andmore amenable to regional cultivation, and also that those sources fromwhich food is not derived may be additionally attractive. Exemplarybiologically-derived oils/oil sources include, but are not limited to,canola, castor, soy, rapeseed, palm, coconut, peanut, jatropha, yellowgrease, algae, and combinations thereof to meet the compositionobjectives. In one embodiment, the fatty acyl mixture is a triglyceridewherein the fatty acid groups have two or three different chain lengthsto meet the composition objectives. In another embodiment, the fattyacyl mixture is a blend of triglycerides to meet the compositionobjectives. In yet another embodiment, the fatty acyl mixture is derivedfrom the at least partial hydrolysis of triglycerides to meet thecomposition objectives.

The hydrolysis, or splitting, of fats/oils to produce fatty acids andglycerol can be achieved by a number of methods: high pressurehydrolysis without a catalyst, medium-pressure autoclave hydrolysis witha catalyst, the ambient pressure Twitchell process with a catalyst, andenzymatic hydrolysis. For more on the hydrolysis of fats/oils see, N. O.V. Sonntag, “Fat Splitting,” J. Am. Oil Chem. Soc., 56 (II), 729A-732A,(1979); N. O. V. Sonntag, “New Developments in the Fatty Acid Industry,”J. Am. Oil Chem. Soc., 56 (II), 861A-864A, (1979); V. J. Muckerheide,Industrial Production of Fatty Acids: Fatty Acids; Their Chemistry,Properties, Production and Uses, Part 4, 2^(nd) ed., IntersciencePublishers, 2679-2702 (1967); and M. W. Linfield et al., “Enzymatic FatHydrolysis and Synthesis,” J. Am. Oil Chem. Soc., 61, 191-195 (1984).

2. Methods: Referring now to FIG. 1, one embodiment of the presentinvention is directed to a method comprising the steps of: (Step 101)providing a fatty acyl mixture comprising: (i) a C₁₀-C₁₆ acyl carbonatom chain content of at least 30 wt. % wherein at least 80% of theC₁₀-C₁₆ acyl carbon atom chains are saturated; and (ii) a C₁₈-C₂₂ acylcarbon atom chain content of at least 20 wt. % wherein at least 50% ofthe acyl C₁₈-C₂₂ carbon atom chains contain at least one double bond;(Step 102) hydrolyzing at least some of the mixture to yield a quantityof C₁₀-C₁₆ saturated fatty acids and C₁₈-C₂₂ unsaturated fatty acids;(Step 103) oligomerizing at least some of the C₁₈-C₂₂ unsaturated fattyacids to yield a quantity of C₃₆₊ fatty acid oligomers; (Step 104)hydrotreating at least some of the C₁₀-C₁₆ saturated fatty acids and atleast some of the C₃₆₊ fatty acid oligomers to yield a quantity ofdiesel fuel blendstock and C₃₆₊ alkanes; and (Step 105) separating atleast some of the diesel fuel blendstock from the C₃₆₊ alkanes.

In some such above-described method embodiments, there is a sub-step ofhydrolysis to yield a quantity of C₁₀-C₁₆ saturated fatty acids andC₁₈-C₂₂ unsaturated fatty acids. Such hydrolysis steps are generallyconsistent with those as described in Section 1.

In some such above-described method embodiments, there is a sub-step ofoligomerization to yield a quantity of C₃₆₊ fatty acid oligomers. Whilenot intending to be bound by theory, the above-described oligomerizationis thought to occur via additive coupling reactions between fatty acidcomponents having regions of unsaturation. Such oligomerization can beeffected via thermal, catalytic, and/or chemical means. Exemplarycatalysts include SiO₂—Al₂O₃, zeolites, and clays, such as bentonite andmontmorillonite. In some such above-described method embodiments, theoligomerized mixture comprises an oligomer component, wherein theoligomer component of the mixture comprises at least about 50 wt. %dimer (dimeric) species (i.e., dimers resulting from the dimerization ofunsaturated fatty acid components). Generally, the oligomerization isconducted over a clay catalyst, in the absence of added hydrogen, at atemperature in range of 300° F. to 700° F. (140° C. to 371° C.), at aliquid hourly space velocity in the range of 0.5-10 h⁻¹, and at apressure such that the feed is in the liquid phase. The oligomerizationmay occur in the presence of added hydrogen provided that ahydrogenating metal catalyst is not present. Methods for theoligomerization of unsaturated fatty acids are well known in the art(see, for example, U.S. Pat. Nos. 2,793,219; 2,793,220; 3,422,124;3,632,822; and 4,776,983).

In some such above-described method embodiments, there is a sub-step ofhydrotreating to yield a quantity of diesel fuel blendstock and C₃₆₊alkanes. Hydrotreating removes oxygen from the fatty acids to produceprimarily a normal paraffin product. Hydrotreating involves ahydroprocessing/hydrotreating catalyst and a hydrogen-containingenvironment. In some such embodiments, the active hydroprocessingcatalyst component is a metal or alloy selected from the groupconsisting of cobalt-molybdenum (Co—Mo) catalyst, nickel-molybdenum(Ni—Mo) catalyst, nickel-tungsten (Ni—W) catalyst, noble metal catalyst,and combinations thereof. Such species are typically supported on arefractory oxide support (e.g., alumina or SiO₂—Al₂O₃). Hydrotreatingconditions generally include a temperature in the range of 290° C. to430° C. and a hydrogen partial pressure generally in the range of 400pounds-force per square inch gauge (psig) to 2000 psig, typically in therange of 500 psig to 1500 psig. For a general review ofhydroprocessing/hydrotreating, see, e.g., Rana et al., “A Review ofRecent Advances on Process Technologies for Upgrading of Heavy Oils andResidua,” Fuel, 86, 1216-1231 (2007). Methods for hydroprocessingtriglycerides to yield a paraffinic product are well known in the art(see, for example, U.S. Pat. No. 4,992,605).

In conventional processes, C₁₈₊ fatty acids are hydrotreated to producea normal paraffin product. The normal paraffin product derived from C₁₈₊fatty acids contributes to pour point problems in diesel fuel. Thenormal paraffinic product derived from C₁₈₊ fatty acids can be furtherisomerized to lower its pour point using an isomerization dewaxingcatalyst. In contrast, the methods of the present invention do notrequire a subsequent isomerization step as the normal paraffin productis derived from C₁₀-C₁₆ fatty acids which contribute less, to verylittle, of a pour point problem in diesel fuel. The elimination of asubsequent isomerization step also reduces cost, since that steptypically requires a separate catalyst bed and/or a separate reactor. Inaddition, the C₁₀-C₁₆ diesel fuel blendstock of the invention can beblended into the diesel pool because the chain lengths are shorter thanthe normal C₁₈₊ products such that the cloud point will be low enough tohave a reduced negative impact on the cloud point of the pool. Byoligomerizing C₁₈₊ fatty acids, this not only contributes to theproduction of a valuable base oil product, but also removes those C₁₈₊fatty acids from the diesel fuel blendstock, minimizing impact on pourand cloud points.

In some such above-described method embodiments, there is a sub-step ofseparation of the diesel fuel blendstock and the C₃₆₊ alkanes. Whilethose of skill in the art will recognize that a variety of separationtechniques can be suitably employed, in some such above-described methodembodiments the separating step comprises distillation. In oneembodiment, the step of distilling employs a distillation column (unit)to separate the C₃₆₊ alkanes and diesel fuel blendstock into individualfractions. Generally, the C₃₆₊ alkanes are collected in a high-boilingfraction and the diesel fuel blendstock is collected in a low-boilingfraction. In some particular embodiments, a fractional bifurcationoccurs at or around 340° C., in which case the diesel fuel blendstock islargely contained within a 340° C.− fraction (boiling below 340° C.) andthe C₃₆₊ alkanes are contained within a 340° C.+ fraction (boiling above340° C.). Those of skill in the art will recognize that there is someflexibility in characterizing the high and low boiling fractions, andthat the products may be obtained from “cuts” at various temperatureranges.

In one embodiment, the diesel fuel blendstock produced comprises atleast 70 wt. % C₁₀-C₁₆ alkanes; in a second embodiment, at least 80 wt.% C₁₀-C₁₆ alkanes; in a third embodiment, at least 90 wt. % C₁₀-C₁₆alkanes.

The cloud point of the diesel fuel blendstock can be determined by ASTMD2500. In one embodiment, the diesel fuel blendstock has a cloud pointof less than −10° C.

In one embodiment, such above-described methods further comprise a stepof hydroisomerizing at least some of the C₃₆₊ alkanes to yield aquantity of base oil blendstock. Generally, the step of hydroisomerizingis carried out using an isomerization catalyst. Suitable suchisomerization catalysts can include, but are not limited to Pt or Pd ona support such as, but further not limited to, SAPO-11, SM-3, SM-7,SSZ-32, ZSM-23, ZSM-22; and similar such supports. In some or otherembodiments, the step of hydroisomerizing involves an isomerizationcatalyst comprising a metal selected from the group consisting of Pt,Pd, and combinations thereof. The isomerization catalyst is generallysupported on an acidic support material selected from the groupconsisting of beta or zeolite Y molecular sieves, SiO₂, Al₂O₃,SiO₂—Al₂O₃, and combinations thereof. In some such embodiments, theisomerization is carried out at a temperature between 250° C. and 400°C., and typically between 290° C. and 400° C. The operating pressure isgenerally 200 psig to 2000 psig, and more typically 200 psig to 1000psig. The hydrogen flow rate is typically 50 to 5000 standard cubicfeet/barrel (SCF/barrel). Other suitable hydroisomerization catalystsare disclosed in U.S. Pat. No. 5,300,210, U.S. Pat. No. 5,158,665, andU.S. Pat. No. 4,859,312.

With regard to the catalytically-driven hydroisomerizing step describedabove, in some embodiments, the methods described herein may beconducted by contacting the product with a fixed stationary bed ofcatalyst, with a fixed fluidized bed, or with a transport bed. In onepresently contemplated embodiment, a trickle-bed operation is employed,wherein such feed is allowed to trickle through a stationary fixed bed,typically in the presence of hydrogen. Illustrations of the operation ofsuch catalysts are disclosed in U.S. Pat. No. 6,204,426 and U.S. Pat.No. 6,723,889.

The viscosity index of the base oil blendstock can be determined by ASTMD2270. In one embodiment, the base oil blendstock has a viscosity indexof greater than 120; in a second embodiment, a viscosity index ofgreater than 130; in a third embodiment, a viscosity index of greaterthan 140.

The pour point of the base oil blendstock can be determined by ASTM D97.In one embodiment, the base oil blendstock produced has a pour point ofless than −10° C.

In one embodiment, the base oil blendstock may be further subjected toan optional hydrofinishing step which generally serves to improve color,and oxidation and thermal stability. In one embodiment, the base oil isutilized as a lubricating base oil blendstock.

For the purposes of this specification and appended claims, unlessotherwise indicated, all numbers expressing quantities, percentages orproportions, and other numerical values used in the specification andclaims, are to be understood as being modified in all instances by theterm “about.” Accordingly, unless indicated to the contrary, thenumerical parameters set forth in the following specification andattached claims are approximations that can vary depending upon thedesired properties sought to be obtained by the present invention. It isnoted that, as used in this specification and the appended claims, thesingular forms “a,” “an,” and “the,” include plural references unlessexpressly and unequivocally limited to one reference. As used herein,the term “include” and its grammatical variants are intended to benon-limiting, such that recitation of items in a list is not to theexclusion of other like items that can be substituted or added to thelisted items. To an extent not inconsistent herewith, all citationsreferred to herein are hereby incorporated by reference.

What is claimed is:
 1. A method comprising the steps of a) providing afatty acyl mixture comprising: (i) a C₁₀-C₁₆ acyl carbon atom chaincontent of at least 30 wt. % wherein at least 80% of the C₁₀-C₁₆ acylcarbon atom chains are saturated; and (ii) a C₁₈-C₂₂ acyl carbon atomchain content of at least 20 wt. % wherein at least 50% of the acylC₁₈-C₂₂ carbon atom chains contain at least one double bond; b)hydrolyzing at least some of the mixture to yield a quantity of C₁₀-C₁₆saturated fatty acids and C₁₈-C₂₂ unsaturated fatty acids; c)oligomerizing at least some of the C₁₈-C₂₂ unsaturated fatty acids toyield a quantity of C₃₆₊ fatty acid oligomers; d) hydrotreating at leastsome of the C₁₀-C₁₆ saturated fatty acids and at least some of the C₃₆₊fatty acid oligomers to yield a quantity of diesel fuel blendstock andC₃₆₊ alkanes; and e) separating at least some of the diesel fuelblendstock from the C₃₆₊ alkanes, wherein the diesel fuel blendstock ofStep e) has a cloud point of less than −10° C.
 2. The method of claim 1,wherein the diesel fuel blendstock comprises at least 70 wt. % C₁₀-C₁₆alkanes.
 3. The method of claim 1, wherein the step of hydrotreatinginvolves a hydroprocessing catalyst and a hydrogen-containingenvironment.
 4. The method of claim 3, wherein the hydroprocessingcatalyst is selected from the group consisting of cobalt-molybdenum(Co—Mo) catalyst, nickel-molybdenum (Ni—Mo) catalyst, nickel-tungsten(Ni—W) catalyst, noble metal catalyst, and combinations thereof.
 5. Themethod of claim 1, wherein the separating step comprises distillation.6. The method of claim 1 further comprising a step of hydroisomerizingat least some the C₃₆₊ alkanes to yield a quantity of base oilblendstock.
 7. The method of claim 6, wherein the step ofhydroisomerizing involves an isomerization catalyst comprising a metalselected from the group consisting of Pt, Pd, and combinations thereof.8. The method of claim 6, wherein the base oil blendstock has aviscosity index of greater than
 120. 9. The method of claim 6, whereinthe base oil blendstock has a viscosity index of greater than
 140. 10.The method of claim 6, wherein the base oil blendstock is utilized aslubricating base oil blendstock.